The present invention relates to a liquid crystal display device for displaying video on a liquid crystal display panel and more specifically to a liquid crystal display device allowing viewers to preset a time to start viewing a video program on the LCD panel screen.
Recent development of lighter and thinner personal computers and television receivers has been accompanied by development of lighter and thinner display devices. To meet the above demand, there have been developed, in place of cathode-ray tube (CRT) type displays, flat panel type displays (FPD) such as liquid crystal display (LCD) devices using LCD panels each having a liquid crystal layer and electrodes for applying data voltages to the liquid crystal layer.
A liquid crystal display (LCD) is a display device capable of providing desirable images by applying data voltages to a liquid crystal layer held between two substrates and controlling the intensity of an electric field to a liquid crystal layer having dielectric anisotropy so as to control the quantity of light passing through the substrates. The liquid crystal display thus constructed is representative of portable flat panel type displays. The most popular display is known as a TFT LCD using a thin film transistor (TFT) as a switching element.
However, it is well known that the liquid crystal has a temperature characteristic featured by extremely low response to an input signal at a low temperature. Recently, liquid crystal displays are not only used as display devices of personal computers but also used as display devices of television receivers and have increasing demand for displaying video programs. However, the response of the liquid crystal decreases at a low temperature, so the LCD suffers such drawback that the quality of a video image displayed thereon extremely decreases at a low ambient temperature, resulting in appearance of afterimage and/or tailing of the image, etc.
To solve the above problem regarding the low response speed of the LCD at a low temperature, Japanese Laid-open Utility Model Publication No. 1-140520, Japanese Laid-open Patent Publication No. 3-33720 and Japanese Laid-open Patent Publication No. 10-228013 propose the provision of a heating element or a heater to promptly improve the response characteristic of liquid crystal at a low temperature by forcibly heating the LCD panel to a temperature at which it can normally work.
Japanese Laid-open Patent Publication No. 10-333124 discloses a liquid crystal display (LCD) wherein, when a signal from a temperature sensor indicates a temperature at which the liquid crystal display element cannot normally operate, then the voltage applied to a white heat valve (light source) is increased to heat the LCD element, thereby improving the response of the LCD element at a low temperature without additional heater such as heating wire element and so on.
However, the above conventional arts prevent the degradation of an image displayed on the LCD by heating the LCD panel when displaying input video after switching on the main power supply but still involve a problem that viewers should view the degraded video on the LCD until the LCD reaches the normal working temperature.